Hey buck Krazy,
It may be spawning burbot making it real murky. Its the right time of year and i've had it screw up fishing before. That or like you said, decay. The perch are really thick at Sherburn if you care to know. I manage 8 (kept 7, had one accidental release after he was in my pile for a few minutes). Saw hundreds with my camera, incredable. Neat to hear the eyes were so shallow, not a bad sign at all. I may have to make a trip out there this season to see them. I saw a big one on my camera at sherburn today but he wasn't worried about my jig, too many little perch to eat.